How to fertilize vegetables without pollution

The principle of fertilization for the production of pollution-free vegetables is: mainly organic fertilizer, supplemented by other fertilizers; mainly by multiple compound fertilizers, supplemented by single element fertilizers; mainly by base fertilizers, supplemented by top dressing. The following principles must be applied to the application of chemical fertilizers: The use of nitrate nitrogen fertilizers is prohibited. If application is required, the amount of fertilizer per acre should be controlled under 25 kg; the fertilizer must be applied in conjunction with organic fertilizer, and the ratio is 2:1. The last time fertilizer is applied The time should be 30 days before harvest. In addition, in the fertilization should also pay attention to the following questions: Human fecal urine should be thoroughly fermented and decomposed, and after flushing, it should be poured with clean water. 2. Fertilizers should be deepened and applied early. Deep application can avoid the volatilization of fertilizers and increase the utilization rate of nitrogen; early application is beneficial to the early growth of the plants and prolong the fertilizer efficiency. Ammonium nitrogen should be applied to soils deeper than 6 cm in fertilization and urea should be applied to soil layers deeper than 10 cm. 3. Should apply biological nitrogen fertilizer, increase phosphorus, potassium fertilizer. The application of biological nitrogen fertilizer can effectively solve the phenomenon of soil compaction caused by the use of chemical fertilizers. Phosphorus and potassium fertilizers have obvious effects on enhancing the stress resistance of vegetables. 4. According to the type of vegetables and cultivation conditions, flexible fertilization. Different types of vegetables have very different levels of nitrate accumulation. In general, the nitrate content in leafy vegetables is higher than that in fruit vegetables. Nitrate content of the same vegetable varies in different climatic conditions. Nitrate is not easy to accumulate under the conditions of high temperature and strong light, and it is easy for nitrate to accumulate under low temperature and low light conditions. Therefore, during the fertilization process, the types of vegetables, cultivation seasons, and climatic conditions should be taken into account to grasp a reasonable amount of application so as to ensure that the nitrate content is controlled within the scope of pollution-free vegetables.